Who knew Nick Jonas had such a buff body? The Jonas Brothers singer, 20, showed off his impressive physique via Instagram on Tuesday. "I never do this, but ..." the pop star wrote in the photo caption. "Healthy living and fitness update. Post workout picture. #diabeticinshape #2.0."

Posing shirtless and exposing his hairy chest, the "First Time" singer struck a seductive pose and flexed his biceps. The image immediately elicited a slew of excited responses from Jonas' fans. "This totally made me feel better after my crappy day at work," one user wrote. Another admirer pleaded, "Marry me and make babies!"

Jonas -- single since his February 2012 split with Australian pop star Delta Goodrem -- has been tweeting about his fitness quest since the spring. "Workout done. Food. Then set," he told his followers on May 10.

Though he hasn't detailed his exact workout routine, Jonas did tell Us Weekly about his healthy eating habits at Z100's Clear Channel radio studios in New York City on July 25. "I love dried kale with seasoning on it," he revealed.